The initial standards for safety of walkers set by the Consumer Product Safety Commission dealt with injuries to the hands from pinching, but did nothing to address the issue of falls. And the majority of the severe injuries occur when the walker goes down the stairs.
About one-fourth of all reported injuries with walkers involved injuries to the head, including fractures. Walkers allow for an infant who isn't normally very mobile to become quite efficient at getting around. So, other injuries including pinched fingers, burns and accidental poisonings have all been reported due to the child being able to get into dangerous areas with lightening speed.
The track record with walkers was so dismal that the American Academy of Pediatrics recommended banning the manufacture and sale of mobile infant walkers. This never occurred, and a response was made in the form of a new standard, adopted as of July 1, 1997. To meet the new standard, the new generation walker must have one of two features. Walkers are now made wider so they cannot fit through most doorways and can stop at the edge of a step.
It's important you understand that these new walker designs will not prevent all injuries from walkers. Because they still have wheels, young children can still move faster and reach higher than they could on their own. A baby in a walker can move three feet in one second, so they are not even safe with close adult supervision.
Parents who are considering toys for infants will find their money best spent on playthings other than walkers. There are stationary walkers that have no wheels, but have seats that rotate and bounce while keeping baby in one spot.
Source: Pediatrics, September, 2001